1. Field of the Invention
This invention relates generally to evaporative filter pads of the type employed in humidifiers and evaporative coolers and particularly to an improved pad having odor-removal characteristics.
2. Description of the Related Art
Evaporative pad filters are typically used in humidifier and evaporative cooling applications wherein the pad is wetted while air is forced through the pad. The outflow air picks up water vapor and is cooled by losing heat during the evaporative process. Depending upon the primary goal, either humidification or cooling is emphasized by the design of the appliance and the ambient conditions of operation of the appliance.
There are several well-known forms of evaporative pads. One of the more popular types typically employed in residential forms of room humidifiers is a pad comprising a plurality of sheets or layers of slit and expanded highly adsorbent wicking paper or thin sheets of aluminum coated with an absorbent material.
The two highly popular forms of wetting of the pad are the drip down or top fed types and the wick-up types. In the former, a constant supply of water is fed to the top of the pad which drips downward via the force of gravity to wet the remainder of the pad. Such pads typically consist of layers of slit and expanded aluminum often coated with particles having absorbent characteristics. In the latter wick-up types, the lower portion of the pad rests in a reservoir of water which is wicked upwards through the pad comprising layers of slit and expanded absorbent paper. However, wicking paper pad could also be drip fed from the top of the pad if desired.
The pads comprising wicking paper have become very popular in home humidifiers and evaporative coolers because of their lower cost and good efficiency. While some prior and current type of evaporative pads have been satisfactory, significant improvements have not been advanced for many years.
One of the problems which arises in connection with appliances using evaporative pads is the presence of some offensive odors from sources in the incoming air flow unrelated to the pads or those which may arise from the evaporative process which takes place in the pad itself.
Bacteria carried by the ambient air passing through the pad are one likely source of odors formed within the pad as the bacteria tend to multiply in the friendly, moist environment formed during use of the wetted pad. While some of these types of pads include one or more layers treated with a bactericide, such a layer primarily reduces air borne microbes contacting the treated layer. However, such a layer has no direct absorption effect of noxious gaseous odors present in the ambient air passing through the pad.
While some prior attempts have been made to address this problem, a satisfactory, economical solution which provides significant odor removal capabilities, particularly to wicking type filters has eluded those of ordinary skill in the art.
In order to be commercially satisfactory, an evaporative pad having significant odor removal capabilities must be economically feasible for wide spread residential use. This includes relatively low cost raw materials and manufacture, minimal rise in pressure drop through the pad, and no significant loss of odor removal efficiency in the wet environment of a humidifiers appliance.